Heretofore, the use of transparencies in military and industrial hardware has required exacting properties for their certified use. For example, a military helicopter having vast areas of transparent material will require special transparent material having identifiable indices of refraction to prevent internal reflection of sunlight. Other transparencies require resistance to penetration by projectiles. Still other transparencies are designed for resistance to abrasion.
The use of these transparencies in military and industrial applications has been severely limited by the temperatures these composite materials could withstand. Direct application of a heat source or a high energy point of origin could quickly alter the physical properties of the composite materials. Whether the thermal effects be generated by fossil fuel fires or laser application, the conventional transparencies lacked sufficient resistance to the intense heat generated. Therefore, the need exists for a material which is heat resistant, in order to complement the impact, ballistic, abrasion, or light resistant materials presently existing in composite transparencies.
Likewise, the use of these transparencies in military and industrial applications has been subjected to irreversible damage caused by the penetration of moisture into the various layers of the composite transparent structure. The susceptibility of these materials to moisture penetration in humid conditions creates a lasting haze within the transparency structure. Further, the materials must maintain adhesion among the various layers and also must maintain modulus values among the various layers at acceptable and constant levels. Therefore, the need exists for a material which is resistant to moisture permeability to protect conventional and heat resistant transparent materials from haze characteristics but further maintains ultimate strength and constant modulus.